1. Field of the Invention
The present invention relates to a projection-type image displaying apparatus including a dustproof unit for preventing dust from entering the apparatus.
2. Description of the Related Art
Recently, the definition of projection-type image displaying apparatuses has been increasing. In such a high-definition image displaying apparatus, noticeable degradation of image quality occurs even if a small amount of dust is carried by cooling air supplied from a cooling unit and adheres to an optical modulator or an optical element disposed near the optical modulator.
Accordingly, a dustproof filter is provided at an air inlet of the cooling air to prevent dust from entering the apparatus. To substantially completely remove dust by the filter, the filter must have a fine mesh. However, when a filter having an extremely fine mesh is used, the filter functions as a resistance to airflow and accordingly the temperature of the overall apparatus is increased. This also leads to degradation of the image quality.
In addition, the dustproof filter becomes clogged with dust as the apparatus is used. Therefore, it is necessary to replace or clean the dustproof filter.
Japanese Patent Laid-Open No. 2002-174855 discusses a structure that can increase the dust collection efficiency. In this structure, a first filter that is cleanable and a second filter that includes a charging member are provided at an air inlet of cooling air. However, in this structure, the first filter and the second filter are disposed outside a cooling fan, which functions as a cooling unit. Therefore, there is a risk that the dust existing in the cooling fan and in a duct that extends from the cooling fan to an optical modulator will adhere to the optical modulator or an optical element disposed near the optical modulator in the duct.
In addition, to replace the second filter with another filter, it is necessary to detach the first filter that is disposed in front of the second filter. Therefore, both of the filters are removed in the process of replacing the second filter, and there is a risk that dust will enter the apparatus during this process.
In addition, Japanese Patent Laid-Open No. 2004-126421 discusses a structure in which dustproof filters are disposed at an air inlet of the cooling fan and in a flow path between the cooling fan and an optical element.